The issue all of you have to take into account is that when running the specified 87 octane the car is NOT running at maximum advanced timing throughout its rpm/load range.

Some RPM/Load conditions will not be retarded very much while others are. The benefit from the high octane gas depends on learning your driving conditions with that gas. It wont be an instant change just by trying a couple gallons.

If the higher octane meant unburnt fuel was sent into the exhaust then the oxygen sensor would see this. The vehicle would lean out and the exhaust temp would raise. This isnt happening.

Once combustion is initiated the energy in the flame is greater than any resistance that 92 octane would have.

Maybe 89 octane is the best balance though.

Too many of you give up easily. You think you are right, which you may be, but you are just going with what you always have been told without looking into it.